Aircraft typically include multiple systems for measuring physical parameters across various parts of the aircraft during flight, from which air flight data, including airspeed, altitude and airframe attitude (pitch and yaw) information, is typically derived. Such multiple systems may include an airframe data system which monitors physical parameters about the body, wings, tail, nacelle of an aircraft to provide an indication of airspeed, attitude, temperature, and static pressure about the aircraft; and an electronic engine control system provides data to regulate the air/fuel ratio distributed to each of the aircraft's engines. The prior art teaches supplementing the information gathered by one system with that of another. For example, in one known approach, the static pressure information provided by an airframe data system is supplemented by the temperature information provided by an engine control system.
Such prior art systems employ a wide variety of sensors, structures and techniques for gathering the desired physical parameter information, including nose-mounted booms, Pitot tubes and flush-mounted static pressure taps, and optical data systems. Each of these prior art systems has its deficiencies or disadvantages.
For example, nose booms, which are generally effective at providing airspeed and altitude information, typically include sensors for measuring static pressure, total pressure and temperature. However, nose booms reduce the aerodynamics of the aircraft, making them impractical to use during normal aircraft flight.
Pitot tubes are also generally effective at providing airspeed and altitude information by measuring static pressure, dynamic pressure and temperature about an aircraft. However, Pitot tubes can not be flush-mounted to the airframe of an aircraft and lose accuracy at speeds below about 20 m/s (about 66 ft/s). Flush-mounted static pressure taps sensor systems are typically mounted to the nose of an aircraft, as well as opposite sides of various aerodynamic surfaces, to measure static pressure, total pressure and differential pressures. Flush-mounted static pressure taps typically require the use of a remotely-located temperature sensor, and the placement of such taps in the nose of an aircraft may effect aircraft radar systems. And, as with Pitot tubes, systems employing flush-mounted static pressure taps similarly lose accuracy at speeds below about 30.5 m/s (about 100 ft/s).
Optical data systems are generally effective at generating airspeed and airframe attitude information by projecting a beam of light ahead of the aircraft. The beam is reflected by atmospheric particles back to an optical sensor. The optical system then infers airspeed and airframe attitude based on the beam measurements. Optical systems are not able to measure either pressure or temperature at the sensing location, requiring the use of additional sensors. Additionally, the electronics packaging for each optical sensor is larger and heavier than traditional sensor electronic packages, requiring additional structural modifications be made to support each optical sensor.